Behavior of bipyridine derivative Cu(I) complexes in donor solvents

Cu(I) complexes are known as highly emissive compounds having interesting fluorescence applications[1].Theluminescence is generated by more intense metal to ligand charge transfer (MLCT) electronic transitions for Cu(I), affording longer excited-statelifetimes compared to transient d-d excited state of Cu(II)[2].Herein we report the behavior of two bipyridine derivative Cu(I) complexes containing phenanthroline and biquinoline ligands, respectively, in donor solvents as dimethylsulfoxide and acetonitrile.The Cu(I) phenanthroline complex (1) is unstable in solution,due to oxidation of Cu(I) to Cu(II) in time, accompanied by change in coordination geometry from tetrahedral to trigonal bipyramidal. The Cu(I) biquinoline complex (2) is more stable in donor solvents,the stability increasing at low temperatures with the stabilization of tetragonal geometry of Cu(I).In case of biquinoline ligand, this kind of geometry is stabilized by the bulky aryl substituentsatαposition with respect to the pyridine nitrogen

New carboxysalicylaldehyde schiff base ligand and its copper(II) complexes

Metal-organic frameworks have become a subject of great interest lately because of their interesting features and applications in the field of catalysis, magnetism and biological studies [1]. Coordination polymers are most commonly the creators of such frameworks, and researchers have devoted great effort to the design of metal-generated networks with tailored properties [2,3]. Our group has recently been involved in the development of by-design structures based on 3d metal coordination complexes derived from Schiff based ligands [4]. Salen-based complexes of 3d metals, in which the Schiff base presents the carboxy substituent on the aromatic moiety, generate infinite coordination polymers in the presence of alkaline bases [5]. In this respect, we have obtained new carboxysalicylaldehyde Schiff base ligand, namely N,N'-bis(5-carboxysalicylidene-aminopropyl)piperazine (CBPP), characterized by NMR and FTIR spectroscopy and TG analysis. Copper(II) complexes of CBPP were synthesized by direct or template synthesis, isolated and characterized by FTIR; preliminary results suggest the formation of polymeric structures

Structural characterization of 3d metal complexes containing an unconventional schiff base ligand

The design of appropriated organic ligands capable of binding metal ions provides a targeted entry to new materials with distinct structural and physicochemical properties. A representative family of such ligands includes Schiff bases. Here, we report new mono, diand polynuclear materials [Co(L)]3(ClO4)3·4H2O (1), [Zn2(L)(CH3COO)2] (2) and [Cu3(L)2(µ3 -ClO4)0.66](ClO4)1.33·1.33CHCl3 (3) containing N,N’-bis[(2- hydroxybenzilideneamino)-propyl]-piperazine (H2L) Schiff base as hexadentate ligand (Figure 1). The X-ray crystallography of the complexes reveal a retaining of the original chair piperazine conformation from the free ligand in the complex 2 and a changing into a boat conformation in the complexes 1 and 3. Moreover, in the respective complexes a different coordination number as 6 (1), 5 (2) and 4 and 5 (3) was observed upon coordination of the free ligand to Co(III), Zn(II) and Cu(II) ions. The modulatory property of H2L is reflected upon the molecular assembly and coordination mode of the isolable species

Synthesis and structural characterization of dimeric and polymeric cooper(II) complexes with schiff base as ligand

Polynuclear coordination compounds derived from multidentate Schiff base ligands are a source of new materials with applications in catalysis [1], optoelectronic materials [2], and environmental applications [3]. In extension of our previous studies [4]on polynuclear materials, we report the crystal structures and spectroscopic properties ofdimeric and polymeric copper(II) complexeswith hexadentate Schiff base N,N’-bis[(2- hydroxybenzilideneamino)-propyl]-piperazine (H2L) as ligand. Reaction of Cu(ClO4)2 hexahydrate with H2L in the presence of triethylamine affords a polymeric structure [Cu3L2(μ3-ClO4)0.66](ClO4)1.33·1.33CHCl3(1) in which the perchlorate anion acts as a tridentate ligand in a μ3-manner binding three Cu3L2 units. When NaN3 was added to the above mentioned reaction mixturea new dimeric assembly[Cu6(C24H30N4O2)4(N3)2][ClO4]2 (2) was obtained in which two azide groups bridge two Cu3L2 unitsin an end-to-end fashion. The same dimeric structure was obtained when the polymer 1 was treated with NaN3

Biocatalytic Route for the Synthesis of Oligoesters of Hydroxy-Fatty acids and ϵ-Caprolactone

Developments of past years placed the bio-based polyesters as competitive substitutes for fossil-based polymers. Moreover, enzymatic polymerization using lipase catalysts has become an important green alternative to chemical polymerization for the synthesis of polyesters with biomedical applications, as several drawbacks related to the presence of traces of metal catalysts, toxicity and higher temperatures could be avoided. Copolymerization of ϵ-caprolactone (CL) with four hydroxy-fatty acids (HFA) from renewable sources, 10-hydroxystearic acid, 12-hydroxystearic acid, ricinoleic acid, and 16-hydroxyhexadecanoic acid, was carried out using commercially available immobilized lipases from Candida antarctica B, Thermomyces lanuginosus, and Pseudomonas stutzeri, as well as a native lipase. MALDI-TOF-MS and 2D-NMR analysis confirmed the formation of linear/branched and cyclic oligomers with average molecular weight around 1200 and polymerization degree up to 15. The appropriate selection of the biocatalyst and reaction temperature allowed the tailoring of the non-cyclic/cyclic copolymer ratio and increase of the total copolymer content in the reaction product above 80%. The catalytic efficiency of the best performing biocatalyst (Lipozyme TL) is evaluated during four reaction cycles, showing excellent operational stability. The thermal stability of the reaction products is assessed based on TG and DSC analysis. This new synthetic route for biobased oligomers with novel functionalities and properties could have promising biomedical applications.</p

Thermal behavior of oligo[(epsilon-caprolactone)-co-delta-gluconolactone] enzymatically synthesized in reaction conditions optimized by experimental design

The thermal behavior of co-oligomers of epsilon-caprolactone (ECL) with gluconolactone, compared to the epsilon-caprolactone oligomer, has been assessed by thermogravimetric analysis, while differential scanning calorimetry was used to evaluate the melting comportment. As the insertion of more hydrophilic structural units can improve the properties and functionalities of the ECL oligoesters, the enzymatic in vitro oligomerization process was optimized by a 3-factorial/3-level experimental design, using the Box-Behnken method. The selected independent variables were the temperature, the enzyme amount, and the molar ratio of monomers, while the co-oligomerization degree and the mass average molecular mass (calculated from MALDI-TOF MS data) were the response variables. The results indicate that temperature has the most significant effect and is directly correlated with the formation of linear co-oligoesters. The overall effect of the other variables was also significant. The thermogravimetric analysis of the co-oligomer synthesized in the optimized conditions indicated a decrease of the thermal stability and compared to the ECL oligomer. Thermoanalytical techniques can consistently improve the utilization efficiency of polymer-based formulations in pharmaceutical and medical applications

Biocatalytic synthesis of poly[ε-caprolactone-co-(12 hydroxystearate)] copolymer for sorafenib nanoformulation useful in drug delivery

Nanoformulations can play an important role in the improvement of anticancer drug therapies. The bioavailability of sorafenib, which is the exclusively applied drug in the treatment of unresectable hepatocellular carcinoma, may be increased by its incorporation in a biocompatible nanoparticulate matrix that is capable of targeting and controlling the drug release. The copolymers of ε-caprolactone are emerging biodegradable compounds for drug delivery applications. In this work, an immobilized lipase and three native hydrolases, a lipase, an esterase and a protease (two of them not previously used as polyesterification catalysts) have been studied as biocatalysts for the synthesis of oligomers of ε-caprolactone and 12-hydroxystearic acid, proving different selectivity regarding the polymerization degree, ratio of linear and cyclic oligomers, and insertion of the fatty acid units in the polymeric chain. The synthesized poly[ε-caprolactone-co-(12-hydroxystearate)] was used as a novel encapsulating copolymer for preparation of sorafenib-loaded polymeric nanocomposites. The nanoparticle formulation by emulsion-solvent evaporation method was optimized for particle size and encapsulation efficiency. The developed nanotherapeutics showed promising drug release profile and cytotoxic effect in vitro in HepG2 hepatocellular cells

Enzymatic synthesis and characterization of novel terpolymers from renewable sources

2,5-Furandicarboxylic acid and itaconic acid are both important biobased platform chemicals and their terpolymer with 1,6-hexanediol (HDO) can be the starting point for a new class of reactive polyesters, with important applications. The green synthetic route developed in this study involves a biocatalytic condensation polymerization reaction of dimethyl furan-2,5-dicarboxylate (DMFDC) and dimethyl itaconate (DMI) with HDO in toluene at 80°C, using commercial immobilized lipases from Candida antarctica B. In the best conditions, the formed polymer product was isolated with more than 80% yield, containing about 85% terpolymer with average molecular mass of about 1200 (Mn, calculated from MALDI-TOF MS data) and 15% DMFDC-HDO copolymer. Considering the higher reactivity of DMFDC, the composition of the synthesized polymer can be directed by adjusting the molar ratio of DMFDC and DMI, as well as by extending the reaction time. Structural analysis by NMR demonstrated the regioselective preference for the carbonyl group from DMI adjacent to the methylene group. The biocatalyst was successfully reused in multiple reaction cycles.</p